The diversity of the HIV virus is a major obstacle to the development of an effective HIV immunotherapy. Several recent studies demonstrate an important role for cell-mediated immunity in both the prevention and control of HIV infection. Failure of HIV-specific immunity has been correlated with "CTL escape" in both primate and human vaccination and immunotherapy studies. Establishment and maintenance of effective CTL- mediated immune responses generally depends on the presence of CD4+ T-cell help, and a Th1 type response is critical for induction and maintenance of cell-mediated immunity. Dendritic cells (DCs) play critical roles in the development and control of immunity. Besides being the most potent antigen-presenting cells (APC), they determine the nature and magnitude of immune responses and provide an essential link between innate and acquired immunity. The studies proposed here will build on our previous efforts utilizing DNA expression constructs encoding autologous patient-derived HIV antigens and novel DC transfection approaches to address major obstacles to effective HIV immunotherapy. Specifically, we propose to genetically engineer skin DCs in vivo to both efficiently present patient-specific Nef and Gag antigens, and express enhanced DC1 type polarized immune-stimulatory function essential for optimal activation of Th1 T- cells in HIV infected individuals. This proposal will develop novel in vivo antigen delivery systems based on the delivery of particulate and DNA formulations encoding HIV-1 antigens to: 1) drive the expression of transgenic (tg) antigens in DCs, 2) favor presentation of tg Ag peptides to CD8+ CTL and CD4+ Th cells and 3) elicit Th1 polarizing DC function. We will test the hypothesis that autologous dendritic cells, genetically engineered to present transgenic patient-derived HIV antigens in the context of Th1 skewing costimulatory function, will induce effective Th1 type patient-specific HIV immune responses. This will be accomplished using both murine models, and unique in situ human skin models we have developed to facilitate translation to clinical trials. In addition to testing this hypothesis, the studies we propose have the potential to overcome major limitations of existing HIV immunotherapies, and to define an immunization strategy capable of containing or eradicating infection in chronically infected patients. Importantly, the studies we propose include translational preclinical models designed as a direct prelude to human clinical trials. PUBLIC HEALTH RELEVANCE: The diversity of the HIV virus is a major obstacle to the development of an effective HIV immunotherapy. We will test the hypothesis that DNA-based immunization strategies that target delivery of autologous antigen to dendritic cells in the context of Th1 skewing adjuvants will induce effective Th1 type patient-specific HIV-1 immune responses. This will be accomplished using both murine models, and unique in situ human skin models we have developed to facilitate translation to clinical trials. The studies we propose have the potential to overcome major limitations of existing HIV immunotherapies, and to define an immunization strategy capable of containing or eradicating infection in chronically infected patients. The studies we propose include translational preclinical models designed as a direct prelude to human clinical trials.